How do you find the exact value of cos (arcsin 3/5 - arccos 1/2)?

Question

5283 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-12-20T14:36:20

#(4+3sqrt 3)/10#.

Let #a=arc sin (3/5) in Q_1 and b = arc cos (1/2) in Q_1#.

Then, #sin a = 3/5 and cos a = sqrt(1-sin^2 a)=sqrt(1-9/25)=4/5#.

Likewise,

#cos b = 1/2 and sin b =sqrt(1-cos^2 b) = sqrt(1-1/4) = sqrt 3/2.#

Now, the given expression is

cos( a - b ) = cos a cos b + sin a sin b

#=(4/5)(1/2)+(3/5)(sqrt 3/2)#

#=(4+3sqrt 3)/10#.